There were unconfirmed reports from Kurdish organisers of serious injuries following three baton charges by officers preventing 200 demonstrators from storming Victorian station.

Trouble flared after more than 2,000 Kurds gathered outside the Home Office in an unofficial protest against the planned extradition to Germany of Kani Yilmaz, the European representative of the Kurdistan Workers Party.

Mr Yilmaz's supporters, who include a number of Labour MPs, believe he will be deported to Turkey from Germany, where he could face imprisonment for his political beliefs. He and other party members have highlighted widespread human rights abuses against the Kurds by the Turkish government.

John Austin-Walker, Labour MP for Woolwich, south-east London, handed in a letter to the Home Office demanding Mr Yilmaz's release on the grounds he is a political prisoner. The Kurdish politician entered Britain in October for talks with Mr Austin-Walker but was arrested as he was about to enter the House of Commons. He has been held at Belmarsh prison, Kent, for six months.

Scotland Yard said last night that a breakaway group of marchers had attacked officers with stones, concrete and placards outside Victoria station, but they were beaten back. Some 250 staged a sit-down protest.

Police said there were four arrests but no serious injuries and no one was taken to hospital.

Kurdish organisers said there were 27 injuries including a man who was critical with head wounds and a girl who had suffered a broken leg. They were unable to say which hospitals the casualties were taken to.